JP3302402B2 - Ammonia decomposition catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ammonia decomposition catalyst capable of performing ammonia decomposition at high pressure and low temperature.

[0002]

[Prior art]

<Ammonia decomposition catalyst> Ammonia is contained in the coke oven gas generated from the coke oven, and is recovered in the process of purifying the coke oven gas. Conventionally, this ammonia was mainly used for producing ammonium sulfate,
If this ammonia is decomposed into hydrogen and nitrogen using an ammonia decomposing catalyst and hydrogen is separated from the decomposed gas, a use with even greater added value can be considered.

[0003] As the ammonia decomposition catalyst, Japanese Patent Laid-Open No.
No. 198639 discloses at least one rare earth element.
An ammonia decomposition catalyst containing a compound of various elements and nickel is shown. Here, compounds of rare earth elements are La ₂ O ₃ , Y ₂ O ₃ , Nd ₂ O ₃ , Sm ₂ O ₃ , Gd ₂ O ₃ , Dy ₂ O ₃ ,
Oxides such as Ho ₂ O ₃ and Er ₂ O ₃ , or inorganic salts such as hydroxides, carbonates and nitrates of rare earth elements, and organic salts such as acetates. As the carrier, alumina, silica gel, silica / alumina, titania, magnesium, activated carbon and the like are used, and alumina is particularly preferred. The catalyst used in the examples is Ni-La ₂ O ₃ -Al ₂ O ₃ , Ni-Y ₂ O ₃ -Al ₂ O
₃ , Ni-Ce ₂ O ₃ -Al ₂ O ₃ (By the way, the catalysts used in the comparative examples are Fe-Al ₂ O ₃ and Pt-Al ₂ O ₃ ). The reaction temperature is 300 to 700 ° C., the reaction pressure may be normal pressure, and the pressure may be increased or reduced. However, in the examples, the reaction is performed at atmospheric pressure.

JP-A-2-198638 discloses an ammonia decomposition catalyst containing nickel and a metal or compound of at least one element selected from a copper group element, a chromium group element and an iron group element. Have been. Here, the copper group element is copper, silver, gold, and the chromium group element are chromium, molybdenum, tungsten, and the iron group element is iron and cobalt. As carriers, alumina, silica gel, silica
Alumina, titania, magnesium, activated carbon and the like are used, and alumina is particularly preferred. The catalyst used in the examples is Ni-Co-Al ₂ O ₃ , Ni-Cu-Al ₂ O ₃ , Ni-C
r ₂ O ₃ -Al ₂ O ₃ (By the way, the catalysts used in the comparative examples are Ni-Al ₂ O ₃ , Fe-Al ₂ O ₃ and Pt-Al ₂ O ₃ ). The reaction temperature is 300 to 700 ° C., and the reaction pressure may be normal pressure.
Although the pressure can be reduced, the reaction is carried out at atmospheric pressure in the examples.

[0005] In the above-mentioned JP-A-2-198639 and JP-A-2-198638, the description of the conventional method is based on the fact that a conventional catalyst for decomposing ammonia is Fe ₂ O ₃ -Al ₂ O.
₃ , NiO-SiO ₂ · Al ₂ O ₃ , Pt-Al ₂ O _{3 and the} like are used, and these catalysts are 500 to 900 ° C., most of which are 700
It is described that the device is used at temperatures up to 1200 ° C.

JP-B-53-7313 (JP-A-52-313)
No. -18485) discloses that the amount of Ni component in the final catalyst is 5.0 to 30.0 wt% in terms of NiO and that the same anion is contained so that the atomic ratio of Mg / Ni is in the range of 0.03 to 0.23. Prepare a mixed solution of salt and Mg salt,
The heat-resistant carrier is immersed in the mixed solution, dried, and dried.
A method for producing a catalyst for decomposing hydrocarbons and ammonia, which comprises calcining at a temperature of 0 to 1100 ° C., is described.
Alternatively, an example in which decomposition was performed at 900 ° C. is shown.

In the description of the conventional method in this publication, a Ni-based catalyst is conventionally used as an ammonia decomposition catalyst. In this case, iron, alumina, magnesium, copper, chromium, It is described that a small amount of a promoter component such as vanadium is added to improve the performance of the Ni-based catalyst, and that the reaction temperature is about 600 to 1000 ° C.

[0008] JP-A-2-284618 discloses that
(A) mixing an oxygen-containing gas composition with an amount of anhydrous ammonia to obtain a gas mixture; (b) heating the gas mixture; and (c) substantially heating all of the heated gas mixture. Contacting with an effective catalyst to decompose ammonia to form hydrogen and nitrogen, whereby the hydrogen reacts with oxygen to form water, thus reducing the oxygen concentration in the gas composition. A method for reducing the concentration of oxygen in an oxygen-containing gas composition, comprising the steps of: Preferred catalysts include “DEOXO LD (major element: A), commercially available from Engelhard Industries.
l >>Pd> Ca, Ga, Re, Cr) ”and“ DE
OXOA (main element: Al >> Pd, Cu, Ga, R
e, Rh, Pt) "it is mentioned, other, iron powder, platinum, platinum alloy, rhodium - platinum alloy, gold - platinum alloy, platinum - palladium - rhodium _{alloy, Fe 2 O 3 -Mn 2 O} 3 - Bi
₂ O ₃ catalyst, cobalt oxide, etc. alone or in combination with other oxides such as iron oxide and chromium oxide, in a supported state or unsupported state (particularly supported on activated alumina,
For example, it is described that it can be used in pelletized palladium on activated alumina). The pressure in the cracking reaction step is from atmospheric pressure to about 20 psig (1.41 atm), preferably 10-15 psig (0.70-1.05 atm) and the reaction temperature is 1500-2000 ° F (815-1093 atm).
° C).

After all, as the ammonia decomposition catalyst, Ni
System; Fe system; Pt system; Pd system; Ni-Mg system; Ni-C
o system; Ni-La system; Ni-Y system; Ni-Ce system; Ni
-Cu; Ni-Cr; etc. are known.

<Separation of hydrogen gas from ammonia decomposition gas> A method of separating hydrogen gas from ammonia decomposition gas is also known. For example, in the embodiment of Japanese Patent Application Laid-Open No. 54-126689, after evaporating liquid ammonia, adjusting the pressure with a pressure reducing valve, introducing the liquid ammonia into a decomposition cylinder filled with a nickel catalyst or the like, and then heating at 900 to 950 ° C. Decompose into hydrogen and nitrogen by reacting, then pass through an adsorption column filled with an adsorbent such as synthetic zeolite to remove undecomposed ammonia and moisture, and 75 kg / cm ² G or more by a compressor, preferably A method is disclosed in which the pressure is increased to 150 kg / cm ² G or more, the liquid is introduced into a gas-liquid separator, and cooled by a cryogen such as liquid nitrogen to liquefy and separate nitrogen. In the description of the conventional method in the publication, there is also a description that it is possible to remove impurities other than hydrogen from the ammonia decomposition gas by the PSA method.

[0011]

The ammonia decomposition reaction is a volume expansion reaction that produces 3 volumes of hydrogen and 1 volume of nitrogen from 2 volumes of ammonia and is an endothermic reaction. Is preferred. In general, low pressure and high temperature reaction is desirable in terms of reaction rate because generated hydrogen generally strongly suppresses the reaction. Therefore, at present, studies under the conditions of low temperature under pressure have not been made. In a typical ammonia decomposition reaction, a nickel catalyst is used at 800 ° C.
React under normal pressure at a moderately high temperature.

However, the reaction under such conditions is disadvantageous in terms of thermal energy due to the high temperature;
Because of the high temperature, special expensive materials such as Inconel must be used for the reactor. In order to separate hydrogen from the obtained ammonia decomposed gas by the PSA method, it is necessary to increase the pressure with a compressor. However, there are problems such as disadvantages in terms of running costs and running costs, etc., and it was not necessarily advantageous from an industrial point of view.

In the inventions of JP-A-2-198639 and JP-A-2-198638, since the catalytic activity is improved based on nickel, the reaction temperature is 300 to 700 ° C, particularly 400 to 600 ° C. Although it has the feature that it can be set to a low temperature of the order of magnitude, in terms of pressure it actually employs atmospheric pressure conditions, and if this is done under pressurized conditions, it is necessary to further improve the catalytic activity . Therefore, when hydrogen is separated from the ammonia decomposition gas by the PSA method, the above problem still remains.

JP-A-2-284618 also uses the normal-pressure high-temperature reaction, and JP-B-53-7313 uses the normal-pressure high-temperature reaction although the catalyst is devised. it is conceivable that.

Japanese Patent Application Laid-Open No. 54-126689 employs a high temperature reaction of 900 to 950 ° C.
This reaction is presumed to be a normal pressure reaction, and furthermore, a method is employed in which the adsorption operation of the ammonia decomposition gas is increased to 75 kg / cm ² G or more, preferably 150 kg / cm ² G or more to perform cryogenic separation. , Industrially disadvantageous.

Under the above-mentioned circumstances, the present invention makes it possible to carry out the ammonia decomposition reaction under high-pressure and low-temperature conditions by utilizing the vapor pressure of liquor (10 kg / cm ² (absolute pressure) at 26 ° C.) Accordingly, an object of the present invention is to provide an ammonia decomposition catalyst capable of separating hydrogen from an ammonia decomposition gas by the PSA method while utilizing the pressure at that time.

[0017]

The ammonia decomposition catalyst of the present invention comprises 5 to 50% by weight of nickel, 2 to 30% by weight of lanthanum as lanthanum oxide, 0.01 to 3% by weight of a platinum group element, and the balance being a carrier. The catalyst comprises a nickel-lanthanum-platinum group element-based catalyst.

Hereinafter, the present invention will be described in detail.

Ammonia decomposition catalyst The ammonia decomposition catalyst in the present invention comprises a nickel-lanthanum-platinum group element-based catalyst. Examples of the platinum group element include platinum, palladium, iridium, ruthenium and the like, and platinum is particularly important.

As the raw material for these metal components, those soluble in solvents such as nitrates, acetates and chlorides for nickel and lanthanum, and chlorides for platinum group elements are used.

As the carrier, silica, alumina, silica / alumina, titania, magnesia and the like are used, and silica is particularly important. When using silica,
It is particularly preferable to use a liquid carrier component such as silica sol or a silica fine powder carrier colloid, whereby the amount of the catalyst component carried can be significantly increased.

The proportion of the catalyst component in the ammonia decomposition catalyst is as follows: nickel is 5 to 50% by weight, particularly 20 to 50% by weight, lanthanum is 2 to 30% by weight as lanthanum oxide, particularly 10 to 30% by weight; When a group element is used, the platinum group metal is 0.01 to 3% by weight, particularly 0.01 to 1% by weight, and the balance is a carrier. If the proportion of the catalyst component is out of this range, the catalytic activity for ammonia decomposition under high pressure and low temperature conditions will be insufficient.

The higher the ratio of the catalyst component to the carrier, the more advantageous the activity. However, when ordinary solid silica, solid alumina or the like is used as the carrier, the amount of the catalyst component carried is limited by the pore volume of the carrier. . However, as described above, when a liquid carrier component such as silica sol or silica fine powder carrier colloid is used, the supported amount of the catalyst component can be drastically increased, and the activity can be improved.

When a solid carrier is used for the ammonia decomposition catalyst, an impregnation method which is a usual production method can be employed. Specifically, the raw materials for the catalyst components are each made into an aqueous solution, and the carrier is separately impregnated and supported, and then mixed, or the aqueous solution in which all the components are mixed is impregnated and supported on the carrier, and then 90 ° C to 150 ° C.
Dried in air for about 12-24 hours, then 400-6
Bake in air at a temperature of 00 ° C for 1 to 10 hours.

When a liquid carrier is used, the catalyst component aqueous solution is mixed with the liquid carrier, evaporated to dryness, and then calcined in the same manner as described above. When the catalyst component-carrier mixture is evaporated to dryness, it may be heated in a laboratory using an ordinary porcelain evaporating dish with an electric heater or the like, and industrially, equipment such as a spray dryer may be used. The aqueous solution of the catalyst component may be treated with an alkali such as ammonia before mixing with the liquid carrier to form a fine precipitate (hydroxide) and then added to the carrier. , May be precipitated and solidified together with the carrier.

In the ammonia decomposition catalyst thus obtained, since the catalyst is gradually reduced during the step of performing the ammonia decomposition reaction, the reduction treatment can be omitted. However, when trying to obtain high ammonia decomposition performance from the beginning of the reaction, it is effective to perform a reduction treatment prior to the reaction. The reduction treatment can be achieved, for example, by performing the treatment in a hydrogen atmosphere at about 400 ° C. for 1 to 10 hours.

Production of ammonia decomposition gas The ammonia decomposition reaction can be carried out according to a conventional method.
The type of reactor may be fixed bed or fluidized bed.

The reaction pressure is at least 2 kg / cm ² or more (usually 5 kg / cm ² or more) and up to about 12 kg / cm ² , especially 1 kg / cm ^2.
It is desirable to be around 0 kg / cm ² . Such a pressure can be easily obtained by vaporizing the introduced liquid ammonia, utilizing the fact that liquid ammonia has a vapor pressure of about 10 kg / cm ² at 26 ° C. If the pressure is too low, the pressure must be increased in the next step, PSA, while if it is too high, it is disadvantageous in terms of reaction rate and reaction equilibrium, and furthermore, in terms of equipment. Since the above-mentioned ammonia decomposition catalyst has a large activity, it can be used even under the above-mentioned high-pressure conditions.

The reaction temperature is desirably set at about 300 to 700 ° C., preferably about 400 to 650 ° C. When the temperature is too low, the reaction does not proceed smoothly, while when it is too high, there is a disadvantage in terms of heat energy and material of the device.

The space velocity (SV) is determined by the reaction temperature and the expected rate of decomposition of ammonia.
It is about h ^-1 ~10000h ^-1. Since the activity of the catalyst is improved by raising the reaction temperature, the reaction can proceed at a higher space velocity under higher temperature conditions. For example, when the reaction temperature is 600 ° C., SV4000
h ^-1 and the reaction temperature of 575 ° C., SV120
The reaction can proceed to equilibrium under a pressure of 10 kg / cm ² even with a load of about 0 h ^-1 .

Separation of Hydrogen Gas from Ammonia-Decomposed Gas After the step of performing the above-mentioned ammonia-decomposition reaction to obtain an ammonia-decomposed gas is performed, the ammonia-decomposed gas is subjected to a PSA process while substantially maintaining the pressure of the preceding process. Separate hydrogen in gas. Unreacted ammonia, if small, is removed with nitrogen in the PSA step without pretreatment.

As the adsorptive separating agent, carbon molecular sieve, synthetic zeolite, natural zeolite, activated carbon,
Or a combination thereof.

In carrying out the PSA step, a plurality of columns are used, and for each column, the pressure raising step, the adsorption step, the pressure reducing step, and the regeneration step are performed cyclically. For example, one column may be in the adsorption step while the other is in the regeneration step. The regeneration is usually performed under reduced pressure. The number of towers is often two to six.

[0034]

The ammonia decomposition catalyst according to the present invention comprises a nickel-lanthanum-platinum group element system. The combined use of the platinum group element improves the catalytic activity as compared with the nickel-lanthanum system, and can minimize the decrease in the catalytic activity of the ammonia decomposition reaction under high pressure.

The ammonia decomposition gas reaction using the ammonia decomposition catalyst of the present invention is performed, for example, at a liquid pressure of about 10 kg / cm ² , which is the optimum pressure in the PSA process. Therefore, in the PSA process, the pressure can be increased by using the pressure in the ammonia decomposition process without performing a special pressure increasing operation, so that a compressor required for the pressure increase is not required and the electric power for operating the compressor is not required. Also becomes unnecessary.

The hydrogen gas obtained through the PSA process can be used as a hydrogen source. For example, by reacting this hydrogen with CO or CO ₂ , it can be used for production of methanol and further gasoline.

[0037]

The present invention will be further described with reference to the following examples.

<Reagents Used> The reagents used are as follows. · Ni: nickel nitrate _{Ni (NO 3) 2 · 6H} 2 O · La: lanthanum nitrate _{La (NO 3) 2 · 6H} 2 O · Pt: platinum chloride (IV) acid _{H 2 PtCl 6 · 6H 2 O} · SiO 2 : No. 1 is a silica sol “Cataloid S-20L” (20 wt% SiO ₂ / water) manufactured by Catalyst Kasei Co., Ltd. No. 2 is a silica carrier “SM” manufactured by Fujimi Abrasives Co., Ltd.
-P31 "・ Al ₂ O ₃ : Activated alumina“ AC
P-1 "

<Production of Catalyst> Using the above reagents as raw materials, an ammonia decomposition catalyst was produced by the following two methods. Table 1 shows the composition of the catalyst and the amount of the reagent used.

No. 1 (using a liquid carrier) A catalyst component salt shown in Table 1 described below was dissolved in water, and the amount of the aqueous solution was adjusted to 100 cc. This aqueous solution was mixed with silica sol, heated on a porcelain dish with an electric heater with stirring, and evaporated to dryness. After drying, the catalyst was calcined at 500 ° C. for 2 hours in a stream of air.

Nos. 2 to 6 (using a solid carrier) The catalyst component salts shown in Table 1 described below were dissolved in water, and the amount of the aqueous solution was adjusted to 12 cc. After putting this aqueous solution into a predetermined carrier,
After drying in a dryer at 120 ° C. for 12 hours, it was baked in air at 500 ° C. for 2 hours.

[0042]

[Table 1] Catalytic assembly formed using a reagent amount _{No. Ni La Pt SiO 2 Al 2} O 3 1 30Ni-20La 2 O 3 -0.1Pt / SiO 2 14.9 5.4 0.03 25 - 2 10Ni-2La 2 O 3 -0.1Pt / SiO ₂ 5.0 0.5 0.03 8.8 − 3 10Ni-2La ₂ O ₃ -0.1Pt / Al ₂ O ₃ 5.0 0.5 0.03 −8.8 4 10Ni-2La ₂ O ₃ / SiO ₂ 5.0 0.5 − 8.8 − 5 10Ni-2La ₂ O ₃ / Al ₂ O ₃ 5.0 0.5--8.8 6 15 Ni / Al ₂ O ₃ 7.5---8.5 (Note 1) No. One catalyst was manufactured using liquid silica as SiO ₂ , and the other catalyst was manufactured using a solid support. (Note 2) No. 1 to 3 are catalysts applicable to the present invention,
Others are catalysts for comparison. (Note 3) The value before each component in the column of catalyst composition is% by weight, and the ratio of the carrier is the remainder. (Note 4) The value of the metal element in the column of the amount of reagent used is the weight of the raw material salt (g), the value of the liquid carrier is the weight as a liquid (g), and the value of the solid carrier is the weight (g) of the carrier itself. .

<Production of Ammonia Decomposition Gas> 1.0 g of the ammonia decomposition catalyst obtained above was made of stainless steel having an inner diameter of 10 mm.
Into a reaction tube of 400 cc / min in a hydrogen stream at 400 cc / min.
Reduction treatment was performed at 2 ° C. for 2 hours.

First, in order to check the ammonia decomposition activity of the above catalyst at normal pressure, normal pressure ammonia gas was passed through the reaction tube at 33 cc / min. The space velocity at this time is 1
It was 200 h ^-1 . Table 2 shows the relationship between the catalyst composition and the ammonia decomposition rate.

[0045]

[Table 2]  Catalyst compositionReaction temperature and ammonia decomposition rate (%) No. 400 ℃ 500 ℃ 550 ℃ 600 ℃ 1 30Ni-20La_TwoO_Three-0.1Pt / SiO_Two 21.3 95.8 99.8 99.9 2 10Ni-2La_TwoO_Three-0.1Pt / SiO_Two 12.1 72.8 − 99.8 3 10Ni-2La_TwoO_Three-0.1Pt / Al_TwoO_Three 6.6 50.0 − 97.0 4 10Ni-2La_TwoO_Three/ SiO_Two 11.2 67.7 − 99.3 5 10Ni-2La_TwoO_Three/ Al_TwoO_Three 6.1 45.3 − 96.4 6 15Ni / Al ₂ O ₃ 6.9 45.2 − 98.8 (Note 1) No. One catalyst is SiO_TwoUsing liquid silica as
Other catalysts are manufactured using solid carriers. (Note 2) No. 1 to 3 are catalysts applicable to the present invention,
Others are catalysts for comparison. (Note 3) The value before each component in the column of catalyst composition is% by weight.
Body proportions are residual.

Next, in order to see the effect of the reaction pressure on the ammonia decomposition activity, 1.0 g of the No. 1, 4 and 6 catalysts among the ammonia decomposition catalysts obtained above were placed in a stainless steel reaction tube having an inner diameter of 10 mm. After filling and reducing in a 100 cc / min hydrogen stream at 400 ° C. for 2 hours, the reaction tube was vaporized with normal pressure ammonia gas and liquor vapor pressure of 10 kg / c.
m ² ammonia gas or a 5 kg / cm ² ammonia gas obtained by adjusting the pressure of the ammonia gas was passed at 33 cc / min. The space velocity at this time was 1200 h ^-1 .
Table 3 shows the relationship between the catalyst composition, the pressure conditions, and the ammonia decomposition rate.

[0047]

[Table 3]  Catalyst composition pressureReaction temperature and ammonia decomposition rate (%) No. force 400 ℃ 450 ℃ 500 ℃ 550 ℃ 600 ℃ 1 30Ni-20La_TwoO_Three-0.1Pt / SiO_Two Always 21.3 57.4 95.8 99.8 99.9 1 30Ni-20La_TwoO_Three-0.1Pt / SiO_Two 5 15.4 44.3 81.1 95.3 99.5 1 30Ni-20La_TwoO_Three-0.1Pt / SiO_Two 10 10.7 31.6 65.9 92.2 99.0 4 10Ni-2La_TwoO_Three/ SiO_Two Always 11.2 − 67.7 − 99.3 4 10Ni-2La_TwoO_Three/ SiO_Two 10 7.6 − 41.4 − 98.1 6 15Ni / Al_TwoO_Three Always 6.9 − 45.2 − 98.9 6 15 Ni / Al ₂ O ₃ 10 4.1 − 27.3 − 96.4 (Note) In the pressure section, “normal” is normal pressure, “5” is 5 kg / cm^Two,
"10" is 10kg / cm^Two.

[0048] Table 3, at a temperature of about 500-550 ° C., in a high pressure such ^{5kg / cm 2, 10kg / cm} 2, it is the ammonia decomposition ratio of the catalyst is also present invention than the conventional catalyst (ammonia conversion) Is high.

[0049]

According to the ammonia decomposition catalyst of the present invention, an ammonia decomposition gas can be efficiently produced even if conditions which are disadvantageous in terms of reaction such as high pressure and low temperature are employed.

The catalyst of the present invention has a high activity,
V operation is possible, so that the throughput per unit time can be increased, the apparatus can be made compact, and the amount of catalyst used can be reduced.

The fact that the ammonia decomposition reaction can be carried out at a high pressure of, for example, about 10 kg / cm ² by utilizing the vapor pressure of liquor is extremely advantageous in performing hydrogen separation by the PSA method in the next step. The compressor cost is reduced. The fact that low-temperature conditions can be adopted is advantageous in terms of heat energy for maintaining the reaction temperature and selection of the material of the reactor.

Therefore, the use of the catalyst of the present invention enables industrially advantageous production of ammonia decomposition gas and separation of hydrogen gas from the decomposition gas.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B01J 21/00-37/36 C01B 3/04

Claims (1)

(57) [Claims] 1. Nickel is 5 to 50% by weight, lanthanum is 2 to 30% by weight as lanthanum oxide, and platinum group element is 0.01 to 50% by weight.
An ammonia decomposition catalyst comprising 3% by weight of a nickel-lanthanum-platinum group element-based catalyst whose balance is a carrier.